1. Field of the Invention
The present invention relates to a manufacturing method for an impeller with which molding and high-quality finishing can be performed extremely easily and quickly through resin molding using a die, and an impeller manufactured by the impeller manufacturing method.
2. Description of the Related Art
Conventionally, a pump such as a water pump is provided with an impeller constituted by a resin impeller main body portion formed with a plurality of vanes, and a metallic bush portion serving as a boss for supporting a drive shaft. Most of these impellers are formed by resin molding using a die. Japanese Utility Model Laid-Open Application Publication 2-18372 and Japanese Unexamined Patent Application Publication H9-217699 exist as examples of impeller products formed by molding resin using a die and a core member.
Japanese Utility Model Laid-Open Application Publication 2-18372 relates to a resin gear apparatus, and discloses an apparatus in which a sleeve metal is fixed in a boss portion as a filler metal. In a molded product molded using a die in this manner, residual resin in an injection gate part of the die forms a mass of resin, and as a result, an unnecessary cladding portion is formed. The unnecessary cladding portion is removed by removal means such as cutting or grinding.
Japanese Unexamined Patent Application Publication H9-217699 discloses an invention in which an insert member is buried in the diametrical direction center of an impeller main body as a boss portion. Likewise in Japanese Unexamined Patent Application Publication H9-217699, finishing is performed by removing cladding portions produced by resin injection through a gate of a die from the gate, and at this time, as described above, removal means such as cutting and grinding are employed. The unnecessary cladding portions in both Japanese Utility Model Laid-Open Application Publication 2-18372 and Japanese Unexamined Patent Application Publication H9-217699 are formed integrally with, and extremely solidly on, the molded product as resin masses.
Therefore, an apparatus or tool for cutting or grinding is required. The unnecessary cladding portion cannot be removed easily, and therefore the removal operation is a completely individual process independent of resin molding using the die. The resulting increase in manufacturing processes leads to a reduction in manufacturing efficiency and an increase in cost. A technical problem (object) of the present invention is to make an operation for removing an unnecessary cladding portion provided in a gate together with a molded main body during molding extremely easy and quick, enabling an improvement in manufacturing efficiency and a reduction in manufacturing cost.
As a result of committed research performed by the present inventor to solve the problem described above, an invention described in claim 1 for solving the problem described above is a manufacturing method for an impeller, comprising the steps of: injecting a resin material through a gate of a die after disposing a metallic bush in the die; forming a thin connecting portion between an unnecessary resin portion formed from residual resin material in the gate and a resin impeller main body molded around the bush; and removing the unnecessary resin portion from the impeller main body using pushing or withdrawing means.
An invention described in claim 2 for solving the problem described above is a manufacturing method for an impeller, comprising the steps of: providing a metallic bush, and a die constituted by a gate side die comprising a gate formed with a flat cylinder-shaped disk gate portion having an inner diameter that is slightly larger than an outer diameter of an axial end portion of the bush and a molding side die having an impeller molding void portion; disposing the bush in the die such that the axial end portion of the bush faces the disk gate portion; injecting a resin material through a gap between the axial end portion of the bush and the disk gate portion; forming a thin connecting portion between an unnecessary resin portion formed from residual resin material in the gate and a resin impeller main body molded around the bush; and removing the unnecessary resin portion from the impeller main body using pushing or withdrawing means.
An invention described in claim 3 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein a position of the axial end portion of the bush is flush with an open surface of the disk gate portion. An invention described in claim 4 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein a position of the axial end portion of the bush is separated from an open surface of the disk gate portion by a slight gap.
An invention described in claim 5 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein a position of the axial end portion of the bush is slightly inserted into the interior of the disk gate portion through an open surface thereof. An invention described in claim 6 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein the axial end portion of the bush is formed with a flat cylinder-shaped circumferential protruding portion, a stepped surface is formed on the outside of the circumferential protruding portion in a lower position than a tip end surface thereof, and the inner diameter of the disk gate portion is slightly larger than an outer diameter of the circumferential protruding portion.
An invention described in claim 7 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein the tip end surface of the circumferential protruding portion is formed flat, and an angle portion between the tip end surface and an outer peripheral side face of the circumferential protruding portion is formed as a right angle. An invention described in claim 8 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein a corner angle portion between the outer peripheral side face and the stepped surface of the circumferential protruding portion is formed with a substantially arc-shaped cross-section. An invention described in claim 9 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein a gap between an inner peripheral side of the disk gate portion and an outer peripheral side of the circumferential protruding portion is smaller than a height of the outer peripheral side face of the circumferential protruding portion.
An invention described in claim 10 for solving the problem described above is the manufacturing method for an impeller pertaining to the above constitutions, wherein the unnecessary resin portion is removed from the impeller main body by pushing a rear surface of the unnecessary resin portion out through a boss hole in the bush in an axial direction using a shaft-like tool. An invention described in claim 11 for solving the problem described above is an impeller manufactured by the manufacturing method.
According to a first exemplary aspect of the invention, the metallic bush is disposed in the die, whereupon molten resin material is injected through the gate in the die. The thin connecting portion is then formed between the unnecessary resin portion formed from residual resin material in the gate and the resin impeller main body molded around the bush, and the unnecessary resin portion is removed from the impeller main body using an impact generated by the pushing or withdrawing means. Since the connecting portion is formed to be thin, the connecting portion can be broken extremely easily by the pushing or withdrawing means, and therefore the unnecessary resin portion can be removed from the impeller easily and quickly. Moreover, since the connecting portion is thin, removal traces of the unnecessary resin portion form a high-quality finished surface, and therefore no post-processing is required on the removal traces.
According to a second exemplary aspect of the invention, the circumferential protruding portion, which has an identical axial center to the boss hole, is formed at the axial end portion of the metallic bush, and the gate on the gate side die of the die is formed with the flat cylinder-shaped disk gate portion having an inner diameter that is larger than the outer diameter of the circumferential protruding portion by a small difference. Hence, the magnitude of the gap between the disk gate portion and the circumferential protruding portion is small, and the connecting portion between the impeller main body and the unnecessary resin portion is formed to be extremely thin when the molten resin material flows into the die and hardens. Accordingly, the connecting portion can be broken extremely easily using the pushing or withdrawing means, and as a result, the unnecessary resin portion can be removed from the impeller easily and quickly. Furthermore, since the connecting portion is thin, the removal traces of the unnecessary resin portion form a high-quality finished surface, and therefore no post-processing is required on the removal traces.
According to the invention described in claim 3, the gap between the disk gate portion and the circumferential protruding portion can be minimized, and the connecting portion can be made extremely thin, making it extremely easy to remove the unnecessary resin portion from the impeller. According to the invention described in claim 4, the connecting portion is formed in the interior of the impeller main body near its surface, and traces of the unnecessary resin portion removed from the impeller can be formed in a slightly recessed form from the surface of the impeller main body. As a result, burrs can be prevented from remaining on the surface of the impeller. According to the invention described in claim 5, the connecting portion can be molded particularly thinly, and therefore the unnecessary resin portion can be removed easily.
According to the invention described in claim 6, the axial end portion of the bush is formed with the flat cylinder-shaped circumferential protruding portion, and the stepped surface is formed on the outside of the circumferential protruding portion in a lower position than the tip end surface. Thus, positioning between the disk gate portion and the axial end portion of the bush can be performed easily, and the gap between the inner periphery of the disk gate portion and the outer periphery of the circumferential protruding portion can be made equal and constant. As a result, the thickness of the connecting portion can also be made constantly thin, and the unnecessary resin portion can be removed from the impeller main body even more easily.
According to the invention described in claim 7, the tip end surface of the circumferential protruding portion is formed flat, and the angle portion between the tip end surface and the outer peripheral side face is formed as a right angle. Thus, the connecting portion between the impeller main body and the unnecessary resin portion also has a right-angled angle portion, and when a pushing or withdrawing force is applied to the connecting portion to remove the unnecessary resin portion from the impeller main body, stress is concentrated in the location of the angle portion such that the connecting portion breaks easily and the breakage traces are comparatively regular.
According to the invention described in claim 8, the corner angle portion between the outer peripheral side face of the circumferential protruding portion and the stepped surface is formed with a substantially arc-shaped cross-section, and therefore, when the molten resin material flows into an impeller molding void portion of the die, the molten resin can be made to flow into the gap formed between the disk gate portion and the circumferential protruding portion in a favorable state. According to the invention described in claim 9, the gap between the inner peripheral side of the disk gate portion and the outer peripheral side of the circumferential protruding portion is smaller than the height of the outer peripheral side face of the circumferential protruding portion, and therefore the connecting portion can be molded to be thinner or smaller (i.e. more fragile) than the other parts. Hence, when removing the unnecessary resin portion from the impeller main body, stress can be applied to the connecting portion easily, and as a result, the connecting portion can be broken more easily.
According to the invention described in claim 10, the unnecessary resin portion is removed from the impeller main body by pushing the rear surface of the unnecessary resin portion out through the boss hole in the bush in the axial direction using the shaft-like tool, and therefore the boss holes serves to guide the pushing operation of the tool, enabling the unnecessary resin portion removal operation to be performed efficiently. According to the invention described in claim 11, the removal traces of the unnecessary resin portion are provided as a high-quality finished surface that does not require post-processing, and therefore an impeller having a favorable finish can be provided at an extremely low cost.